Tire cover



United States Patent Inventor Henri Verdier Puy-de-Dome, France Appl. No. 775,335 Filed Nov. 13,1968 Patented Dec. 15, 1970 Assignee Compagnie Generale Des Etahlissements Michelin, raison sociale Michelin 8r Cie Clermont-Terrand, Puy-de-Dome, France Priority Nov. 15, 1967 France No. 1893 TIRE COVER 9 Claims, 1 Drawing Fig.

US. Cl 152/209 Int. Cl 1360c 11/08 [50] Field of Search 152/209 [56] References Cited UNITED STATES PATENTS 2,324,996 7/1943 Cohen l52/209 2,626,649 l/l953 Eiler et al. 152/209 Primary Examiner-Drayton E. Hoffman An0meyBrumbaugh, Graves, Donohue & Raymond ABSTRACT: A tire cover for running on loose and soft ground is formed with V-shaped bars opening inthe forward direction and arranged in a staggered pattern around either side of the median plane. The bars are so shaped and positioned as to compress and dry wet soil and automatically to expel, when the tire is run momentarily in the reverse direction, any soil that may be caked between them.

PATENTEU DEC] 5 I970 5 1 INVEN'IOR, HENRI VERDIER WM, A

his ATTORNEYS TIRE COVER BACKGROUND OF THE INVENTION This invention relates to tire covers and, more particularly, to novel and highly-effective tire covers having outstanding traction on loose and soft ground.

lt is well known that, for rolling over loose and soft ground, tires are used the tread of which comprises two rows of sharply projecting bars, arranged obliquely, forexample, at 45, and staggered on either side of the median plane. However, the effectiveness of these bars is limited greatly. The spaces between bars have a tendency to become filled with earth adhering to the tire. Consequently, the tire behaves like a tire with ,a smooth tread and starts to slide and sink into the ground; moving, both forward and in reverse, becomes impossible. Numerous attempts to improve the arrangement and the shape of the bars have not heretofore resulted in ;substantial improvement so that, for travel on certain kinds of ground, caterpillars must be used as a remedy. 1

SUMMARY OF THE lNVENTlON An object of the present invention is to eliminate these disadvantages and to provide a tread with bars that assure a better grip on loose and soft ground by'compacting of the ground and by drying up of the earth retained between bars. A further object is to make it possible, by moving the vehicle backward, to expel the earth progressively accumulated between the bars.

The tire cover in accordance with the invention comprises in its tread two rows of sharply projecting bars arranged in a staggered pattern on either side of the median plane. Each row covers substantially halfof; the width of the cover, and each bar has the form of a V open in the forward direction. The branch of each V adjacent to the median plane is inclined approximately 45 with respect to the medianplane, while the other branch of each V has a more pronounced crosswise direction and preferably forms an angle of approximately 65 with the direction of the circumferenceI Each bar comprises on its back surface, adjacent to the shoulder of the tire, an

extra thickness thatincreases in the direction from the peak toward the base of the bar thereby reducing the space between the axially-outer ends of the bars.

BRIEF DESCRIPTION OF THE-DRAWING Additional aspects of the invention may be understood from a consideration of the following detailed description of a representative embodiment thereof in: conjunction with the appended drawing, wherein thesole H0. is a perspective view of a representative tire cover in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The drawing shows a tire cover l having sidewall 2 another sidewall (not visible) opposite the sidewall 2, and shows a crown 3. Thetread of the cover comprises 36 barsof which bars 4, 5, 6 are examples. There are l8 bars identical to bars 4 and 5 disposed in onerow and, forming another row, l8 bars identical to bar 6 and mirror images of the bars 4'and 5. Each bar 6 is placed between two bars 4 and 5, and a space 7 is delimited by the bars 4, 5 and 6. Each bar comprises a portion 8 inclined at an angle of 45 to the rolling or longitudinal direction and a portion 9 inclined atan angle of 65 to the rolling direction, as shown in the drawing. These two portions give each bar the shape of a V open in theforward direction: i.e., a V the inner surface 10 of which is the first one to touch the ground in forward movement (indicatedby an arrow A). Each bar furthermore comprises an extra thickness of pyramidal shape 11 on its back surface 12 in the region of the shoulder narrowing the space between two consecutive bars, such as 4 and 5. As may be seen, the bars touch at 13, a point located at about midheight of .the sidewall 2. Furthermore, the tip 14 of the bar 5 is close to the bar 6, and the tip 15 of the bar 6 is close to the bar 4. The passages between the bars 4 and 6 or 5 and 6 are narrower than the thickness of each of the bars measured perpendicularly to its outline. The circumferential space between-the bars 4 and 5 is approximately three times the circumferential thickness of these bars- The height of the bars exceeds their thickness. r

The relative movements of the bars 4, 5, 6 when passing over the ground result in that the lateral openings of the compartment 7 are closed and in that the earth when wet is pressed like a sponge, whereby it is compressed and dried underneath the tire which thus can better grip the. ground. However, it cannot be avoided that sometimes the earth adheres to the bars and finally comes to fillthe space 7. In such a case, the movements, while rolling backward (opposite the direction indicated by the arrow A), of thecarcass 3 and the bars 4, 5 loosen the earth, which is subsequently ejected. The loosening and ejection result from an abrupt release of pressure by the pyramid-shaped wedge 11 and from the very rounded cross section of the crown 3.

Thus, it will be seen that the representative tire cover described above is preferably characterize'din the following ways:

a. The portion of each bar 4, 5, 6 inclined at 45 covers substantially half of the half-width of the tread while the portion of each bar running at a 65' angle covers substantially the other half of the same half-width of the tread.

b. The thickness of each bar 4, 5, 6, measured perpendicularly to each bar, is substantially constant outside the area of the extra-thick axially-outer end. Measured in the direction of the circumference, the thickness is approximately one-third of the circumferential space between two successive bars.

c. The passages between the portions-inclined at 45 and situated on either side of the median plane of the tire are perpendicular to each other and have a width that is less than the thickness of the bars 4, 5., 6.

d. The bars 4, 5, 6 extend laterally or axially beyond the outer limit of each sidewall and join at approximately midheight of each sidewall at their triangular bases.

e. The cover 1 comprises a total of at least 36 bars, half on either side of the median plane.

. The tire is a radial-carcass-type tire, and its peak reinforcement has a transverse curvature instead of being practically cylindrical. j

g. The carcass, whether of the radial or the crossed kind, has

' a comparatively round cross section. The ratio l-l/B between the height H and the maximum width B of the carcass is at least 0.9 and preferably close to l.

The V-bars 4, 5, 6 in accordance with the invention form the borders of cells 7 the lateral openings, of which are narrow. The deformation of the tread in the ellipse of contact with the ground produces a drawing together of the bars in contact with the ground. When the cover rolls forward i.e., in a manner whereby the surface of the bars first to come in contact with the ground is the inner surface of the V the deformation of the bars produces an additional narrowing, almost a closing of the lateral openings. The earth caught between two successive bars (4 and 5, for example) iscompressed in the direction of the bar (6, in the same example) closing the cell space 7 on the side thereof adjacent to the median plane, while the water wrung out is expeiled laterally. When the tire rolls backward, the orientation of the branches of the Vs with respect to the direction of rolling creates a tendency to loosen and to shift the earth in the direction of the sidewalls. The movements of the carcass after its rolling through the footprint of the tire and of the bars after their deformation by contact with the ground are more violentby reason of the buttressing effect of the bars produced by the extra thickness 11 provided at the base of each bar-on its rear surface, which facilitates the loosening and expelling of the earth.

Thus there is provided in accordance-with the invention a novel and highly-effective tire cover'adapted for use under conditions such that, heretofore, only a caterpillar tread would serve.

1 Theinventioniienotexeeeded modification -eler'nents in relief); thegreaofthe recessed" portionsof the ftreadlPreferablyi theijarea of: they surfaces of all the 7 v is substant a ly m eurth .oft e surface. are eeo'ver l lhk m;1P ;i n the.eircurnferentialspac- *ing of isstlbstantillly -three tithes the circumferential 'ckness of the; bars. Finally; the barslcanibeof variable cirmm flt kknmo have-a m e; pren une d n v i angle ofrtapemv'ithrcspectztoithe carcass.

. :A tire v'MNe1 wl ilprisinga paireotisidewalls. and a tread portion joined to and extending between said sidewalls, two

I of v y-r iec i e ars disposed in staggered relation I -around said tire, cover andtformillg-a :tread,said rows being on ;opposite sides of the. median plane of the tire and each row stibsvstntially;half the width of-the cover, each bar glia'ving the shape of agv open in thet iorward direction, the

liiranch oLeach-Y .adjace'ntto themedian; plane being inclined to that-plane by, about? and the other branch of teach extending in tamore nearly transverse direction and.

e! in; injngle of about 65 .with the directionof the circumso thateach of; the ,four branches extends in a rdilferent-trom the direction in' which every one of b hes extendsaandea iharf bmp ins. 'nl-it rsu'rfmpa ia entito theshou m thee v a' e tra :ihiekne'u incteui g inredireetion-zfrornthe peak toward the lhe' bnrwin, such, a manner-as to reduce the space .-i'ormlng cells whkmduring rolling of said tire cover over w'et -19;facilitlteacompression.oisaicl-soil and'a wringing out-of flif therefrom in order-to. eqnsqlidatesaidsoil and improve athe traction of said tirecover.

1 -2. A the cover-accordingto; claim 1 wherein the two branches ofeach-bar extend over. substantially equal widths of the tread. v I

3. A-tire cover aceording-toclairn 1 wherein the bars of one row and the bars of theotherrowdefine passages-adjacent to the ,median plane of the cover; having a widthiless than the thicknessofthe bars. l t :4. A tirefeoyer according ttoclairnlwhereiri; the bars ofa given row are joined by saidextra thieltnessat about mid sidewall.

i 5. A tire 1 co,v, er according to; claim: .height'tomaximum widthof saidcover rein" the ratio of olive 0.09.

; heightto magtirnum width ofsaidcoyer is about l .0.

7.. A tire cover according to claim l twherein said cover is of the radial typetand is formedwith-a strongly-curved crown.

. 8. A, the cover accordingwto clairr 1 wherein the total --numb er;of bars isat least, 3,6,]of which half are on either side of .the medianplane.

'9. A tire cover-comprisingapair of sidewalls and a tread portion .joinedjtoand,extending between said sidewalls, two 'rowsof sharply projecting-bars disposed-in staggered relation -.around said tirecover and forming a tread, said rows being on oppositesides ofthe median plane or the tire and each row covering; substantially half thewidth of the; cover, each bar ,having the shape. of a .V open, in the forward direction, the branchofeachv adjacentrto the medianplane being inclined ;with respect1to .that plane byabout 45. and the other branch of each 1V extending in atmor e nearly transverse, direction and forming an angle of about 65,with the direction of the circum- 'rt'erence andieach barcornprising, onqits back surface, adjacent t0 the shou'lderof the cover, aneittra thickness increasinginagdireetion-fromtheapeak toward the haseof the bar, in

qsuehxarmannerasrto reduce thespace between the ends of the 35 pbarsa gfilacent to the shoulder; the total area of-the V surfaces loftall} eg-,bars;.bein g-substantially one'fourth oithe surface area of thewidth ofthe cover over. which the bars are placed and the circumferential spacing of the bars being substantially three times the circumferential thickness of the bars.

2 3 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 35171175 Dated December 15, 1970 Invent0r(s) Henri Verdier It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 29, "in" should be an (amendment filed. March 13, 1970, claim 1, line 12); and

Column L, line 12, "0.09" should be 0.9 (application claim 6, line 3).

Signed and sealed this 22nd day of June 1971.

(SEAL) Attest:

ED L'JARD FLFIETCHER, JR. WILLIAM L. SCHUYLER, JR. Attesting Officer Commissioner of Patents 

